System and method for providing automatic data restoration after a storage device failure

ABSTRACT

A system and method for providing automatic data restoration after a storage device failure are disclosed. An agent module detects a failure at a logical unit located at a primary storage device. The agent module locates backup data from the failed logical unit that is stored on a backup storage device and transfers the backup data from the backup storage device to a spare logical unit located on the primary storage device. The agent module then maps the spare logical unit to an address associated with a host in response to detecting the failure at the logical unit.

TECHNICAL FIELD

This invention relates in general to the field of storage systems, andmore particularly to a system and method for providing automatic datarestoration after a storage device failure.

BACKGROUND

The demand for data storage protection and capacity in computernetworking environments increases substantially each year. Internet useand data-intensive applications, such as multimedia and onlinetransaction processes, have contributed to the increased demand for datastorage capacity. Users are also demanding faster access to the data andthe ability to share pooled data among a large number of users overdistributed locations. In addition to these demands, many networkadministrators desire the ability to efficiently change the amount ofstorage available on a network and provide maintenance to the existingstorage.

Today, the computer industry is turning to storage area networks (SANs)to meet demands for increased storage capacity and more rapid access todata. A conventional SAN typically includes a collection of data storagedevices interfaced with one or more servers or workstations. Many SANsuse Fibre Channel (FC) technology in order to transmit data at higherrates. FC devices are generally based on Fibre Channel Protocol (FCP),which may support multiple protocols including Small Computer SerialInterface (SCSI), Asynchronous Transfer Mode (ATM), Transmission ControlProtocol/Internet Protocol (TCP/IP), High Performance Parallel Interface(HiPPI), Intelligent Peripheral Interface (IPI) and others.

In the event that a storage device containing a server boot partitionfails, a system administrator must manually bring the server backonline. In order for the system administrator to restore the data fromthe failed storage device, the system administrator first must benotified of the failure. The system administrator must then determinewhich storage device failed and locate a spare storage device on thenetwork. Finally, the system administrator must manually restore thedata to the spare storage device by using the backup data from thefailed storage device and assign the spare storage device to the serverso that the server has access to the restored data. The process is notonly time consuming for the system administrator but can waste time forusers on the network since the system administrator may not be able tocorrect the problem immediately after the failure occurs.

To eliminate the manual restoration process, data partitions in a SANmay be mirrored. The mirroring technique requires that each host on thenetwork store data on a primary storage device and a backup storagedevice. Mirroring, therefore, requires twice the number of storagedevices than a SAN without mirroring. Furthermore, since the host muststore data in at least two storage devices, the speed of the network maybe effected.

SUMMARY

In accordance with teachings of the present disclosure, a system andmethod are provided that substantially eliminate or reduce disadvantagesand problems associated with data restoration after a storage devicefailure. In one embodiment, an agent module automatically transfers datafrom a backup storage device to a spare storage device in response todetecting a failure at a primary storage device assigned to a host andmaps the spare storage device to the host associated with the primarystorage device.

More specifically, an agent module receives notification from aredundant array of independent disks (RAID) device that a failureoccurred at a logical unit assigned to the host. The agent module theninstructs a backup server to transfer the backup data associated withthe failed logical unit, which is located on a backup tape drive or datadepository, to a spare logical unit that is configured by the agentmodule in response to detecting the failure. When the data transfer iscomplete, the agent module maps the spare logical unit to an addressassociated with the host that owned the failed storage device. The agentconfigures the spare logical unit so that the spare logical unit appearsto the host as the original logical unit. If the host must be rebootedbefore it may access the spare logical device, the agent instructs thehost to reboot. Otherwise, the host accesses the spare logical unit whenthe agent completes mapping the spare logical unit to an addressassociated with the host.

Important technical advantages of certain embodiments of the presentinvention include an agent module that automatically restores data whena storage device failure is detected. The agent module monitors thehosts and storage devices interfaced with a network. If the agent moduledetects a failure on one of the storage devices, the module identifies aspare storage device located on the network, transfers backup dataassociated with the failed storage device from a backup storage deviceto the spare storage device, and remaps the spare storage device to thehost. The agent module, therefore, restores the data from the lastbackup of the failed storage device without any human intervention.Furthermore, since the agent module may immediately begin therestoration process, services provided by the host may only beinterrupted for a very short period of time.

Another important technical advantage of certain embodiments of thepresent disclosure includes an agent module that eliminates the need formirroring from applications that require the immediate restoration ofdata. Mirroring typically requires that at least two storage devices beassigned to a single host. In the present invention, the agent moduleinterfaces with a backup server that has access to a backup storagedevice, such as a high speed tape drive. During normal operation, thebackup server transfers backup data from storage devices interfaced witha network and assigned to a host onto the tape drive. When one of thenetwork storage devices fails, the agent module instructs the backupserver to transfer the data from the tape drive on to a spare, or newlyconfigured, storage device. The agent module, therefore, reduces theneed for additional storage devices and increases the speed of theoverall network.

All, some, or none of these technical advantages may be present invarious embodiments of the present disclosure. Other technicaladvantages will be readily apparent to one skilled in the art from thefollowing figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 illustrates a block diagram of a storage area network forproviding automatic data restoration after a storage device failureaccording to the teachings of the present disclosure;

FIG. 2 illustrates a block diagram of a SAN appliance including an agentmodule that automatically restores data after a storage device failure;and

FIG. 3 illustrates a flow diagram for providing automatic datarestoration after a storage device failure.

DETAILED DESCRIPTION

Preferred embodiments and their advantages are best understood byreference to FIGS. 1 through 3, wherein like numbers are used toindicate like and corresponding parts.

FIG. 1 illustrates a block diagram of computer system 10 for providingautomatic data restoration after a storage device failure. In theillustrated embodiment, system 10 includes SAN appliance 12, storagedevice 14, host 20 and server 22 interfaced with network 26. Storagedevice 24 may be coupled to server 22 though direct communicationslinks, including, but not limited to, Transmission ControlProtocol/Internet Protocol (TCP/IP), Ethernet, InfiniBand, parallelSmall Computer System Interface (SCSI), Advanced Technology Attachment(ATA), Universal Serial Bus (USB) or Fibre Channel Protocol (FCP). Inone embodiment, host 20 may be assigned to store data on logical unit 16located on storage device 14. If a failure occurs at logical unit 16, anagent located in SAN appliance 12 detects the failure at logical unit16, unmaps logical unit 16 from host 20, configures logical unit 18 onstorage device 14, locates data associated with logical unit 16 onstorage device 24, instructs server 22 to transfer backup data fromstorage device 24 to logical unit 18, and maps logical unit 18 to anaddress associated with host 20. The agent, therefore, restores datawithout any intervention by a system administrator.

Network 26 may be a storage area network (SAN) that includesconventional networking components compatible with Ethernet, FCP,InfiniBand and SCSI standards. In alternative embodiments, network 26may be a local area network (LAN), wide area network (WAN), a wirelessnetwork or any other suitable network that is compatible with FCP, SCSIand additional protocols and standards. A SAN may be defined whenphysical storage device sharing is enabled, such as through fibrechannel loops, and hubs or switches. Each device interfaced with a fibrechannel network may be referred to as a node. Nodes that generate dataand seek to store that data, such as workstations, servers andstand-alone personal computers (PCs), may be known as hosts ororiginators. Nodes that act as data storage devices, such as diskstorage, tape drives, or redundant array of independent disks (RAID)devices, may be known as targets or responders.

A SAN may use different types of topologies, including, but not limitedto, point-to-point, switched fabric, arbitrated loop and any otherappropriate combinations of these topologies. In the point-to-pointtopology, nodes are connected by direct connections through a node portlocated in each of the devices. In the switched fabric topology, one ormore electronic switching devices may be included that provide multiple,simultaneous, point-to-point connections between node pairs. In thearbitrated loop topology, devices may connect to the network via a loopport. A hub may be added in the arbitrated loop topology to connectmultiple nodes to one loop and allow devices to be added or removed fromthe loop with minimal disruption to the network.

Fibre channel technology allows data and network protocols to coexist onthe same physical media. In one embodiment, the physical media may be atwisted pair copper cable used for the public switched telephone network(PSTN). In other embodiments, the physical media may be fiber-opticcable if the distance between nodes is too large for copper cable. TheFCP-SCSI command set protocol may be used to interface hosts, such asservers and workstations, with targets, such as conventional storagedevices and RAID devices. FCP-SCSI commands allow storage and retrievalof data to and from the host server and the target storage device asthough the storage area network is simply a SCSI device interfacedthrough fibre channel fabric. In alternative embodiments, network 26 mayuse FCP-IP, FCP-VI or any other suitable command set protocol foraccessing and storing data.

System 10 includes host 20 that communicates with and transfers data toand from storage device 14 through network 26. For example, host 20 mayuse storage device 14 as local storage even though storage device 14 isremote from host 20. As described above, FCP supports SCSI protocolsthat allow host 20 to treat storage device 14 as localized storage. Host20 may be a server, workstation, stand-alone personal computer (PC) orany other suitable computing platform that may execute variousapplications and store data associated with those applications atstorage device 14.

Storage device 14 may be the primary storage device for hosts interfacedwith network 26. Storage device 14 may be one or a collection of harddisks, RAID devices, optical or magnetic medium or any other suitabletype of non-volatile storage. Storage device 14 may further be groupedinto one or more volumes or logical units and each volume may beassigned a logical unit number (LUN) address. For example, in the SCSI-2protocol, storage device 14 may be partitioned into eight differentLUNs. In the SCSI-3 protocol, a sixty-four bit identifier is used toaddress the LUNs in storage device 14. Therefore, although storagedevice 14 includes logical units 16 and 18 that respectively correspondto LUN addresses LUN_0 and LUN_1, any number of LUN addresses may beassigned to storage device 14 by a vendor. Host 20 may then use theassigned LUN addresses to access storage device 14. The availablephysical storage of storage device 14, therefore, is mapped into aplurality of logical unit devices. Logical units 16 and 18 (generallyreferred to as logical units 16) may be accessed through one or moreports on storage device 14 and may provide virtual storage for network26. Although system 10 is illustrated in FIG. 1 as including one storagedevice, system 10 may include multiple storage devices at distributedlocations on network 26 and/or multiple physical storage devices withinstorage device 14.

System 10 also includes server 22 that transfers data to and fromstorage device 14 and storage device 24. For example, during normaloperation of system 10 data may be transferred between host 20 andlogical unit 16. At predetermined time intervals, such as every hour orat a specified time every day, server 22 may access storage device 14and copy the data on logical unit 16 to storage device 24. In this way,server 22 performs a back up of the data on logical unit 16 and thebacked up data may be used if there is a storage device failure insystem 10. In one embodiment, storage device 24 may be a high-speed tapedrive. In other embodiments, storage device 24 may be one or acollection of hard disks, RAID devices, optical or magnetic medium orany other suitable type of non-volatile storage.

System 10 further includes SAN appliance 12 that interfaces with othercomponents, such as storage device 14, host 20 and server 22, vianetwork 26. In one embodiment, SAN appliance 12 may be implemented ashardware and/or software executing on a computing platform, such as astand-alone PC, a workstation or a server. In other embodiments, SANappliance 12 may be hardware and/or software executing on othercomputing platforms that are part of network 26, such as host 20, aswitch in network 26 or on storage device 14. The SAN appliance softwareor logic may be embodied in drives, diskettes, CD-ROMs, DVD-ROMs,optical or magnetic media, field programmable arrays, embeddedprocessors or any other suitable media. In the illustrated embodiment,system 10 uses an outband configuration since SAN appliance 12 islocated outside of the data stream communicated between host 20 andstorage device 14. In an alternative embodiment, system 10 may use aninband configuration where SAN appliance 12 is located inside of thedata stream. In this example, the data transferred between host 20 andstorage device 14 passes through SAN appliance 12.

In operation, SAN appliance 12 includes an agent that monitors storagedevice 14 for failures on logical unit 16. When logical unit 16 isconfigured on storage device 14, SAN appliance 12 maps logical unit 16to host 20 and any other hosts coupled to network 26. In one embodiment,SAN appliance 12 may assign logical unit 16 the LUN address of LUN_0 andlogical unit 18 the LUN address of LUN_1. SAN appliance 12 then mapsLUN_0 to host 20 by assigning the address associated with host 20 tological unit 16. In one embodiment, the host address may be a fibrechannel world wide name (WWN), which is an eight byte unique identifier.The Institute of Electronics Engineers (IEEE) assigns blocks of WWNs tomanufacturers so manufacturers can build fiber channel devices withunique WWNs. In alternative embodiments, the address may be an IPaddress, an Ethernet address or any other suitable address thatidentifies the location of host 20 on network 26.

During normal operation of system 10, the agent in SAN appliance 12monitors network 26. If the agent detects a failure at storage device 14in logical unit 16, the agent locates a spare logical unit andconfigures the spare logical unit for use by host 20. In one embodiment,the agent may determine that logical unit 18 has not been assigned toany host and may be used as the spare logical unit. The agent mapslogical unit 18 to server 22 and/or directly access storage device 24 toobtain the backup data associated with logical unit 16 and transfers thebackup data from storage device 24 to logical unit 18. Once the transferof data is complete, the agent maps logical unit 18 to the addressassociated with host 20. Host 20 may then access logical unit 18. In analternative embodiment, host 20 may be executing an operating systemthat requires host 20 to reboot in order to access logical unit 18. Forthese operating systems, SAN appliance 12 configures the agent toremotely initiate a reboot of host 20. Once host 20 completes the rebootprocedure, host 20 continues normal operation by storing and accessingdata on logical unit 18. Logical unit 16 subsequently may be restored orrepaired and the agent and/or SAN appliance 12 may recognize logicalunit 16 as a spare logical unit.

FIG. 2 illustrates a block diagram of SAN appliance 12. SAN appliance 12may include interface 30, agent module 32 and memory 34. Interface 30may be a physical port, virtual port, or other suitable direct orindirect connection that allows communication with storage device 14,host 20 and server 22 over network 26. Interface 30 may also couple SANappliance 12 to other networks, such as Internet Protocol (IP) networks,Asynchronous Transfer Mode (ATM) networks, Frame Relay networks, FibreChannel networks and any other networks that communicate data. Agentmodule 32 is coupled to interface 30 and may be software executing onone or a combination of microprocessors, microcontrollers, digitalsignal processors (DSPs), or any other digital circuitry configured todetect a failure at storage device 14 and replace the failed logicalunit with a spare logical unit. In an alternative embodiment, agentmodule 32 may be one of the hardware components within SAN appliance 12.Memory 34 stores data and/or instructions generated by agent module 32and may be any suitable form of a volatile or non-volatile memory thatis integral or separate from SAN appliance 12.

In operation, agent module 32 monitors network 26 and detects failuresat logical units 16 on storage device 14. If storage device 14determines that either of logical units 16 has failed, storage device 14generates a failure message and sends the message to SAN appliance 12.The message may be a SNMP message, an Extensible Markup Language (XML)message or any other suitable message that may be generated and sent toSAN appliance 12 over network 26. SAN appliance 12 receives the messageon interface 30 and communicates the message to agent module 32. Uponreceiving the failure message, agent module 32 locates and configures aspare logical unit for use by host 20. In one embodiment, agent module32 instructs storage device 14 to determine if one of logical units 16is not assigned to a host and configure the unassigned logical unit. Inanother embodiment, agent module 32 may instruct storage device 14 toconfigure a spare logical unit that has a storage capability similar tothe failed logical unit from storage media that is not being used bynetwork 26.

After the spare logical unit is configured, agent module 32 restoresdata originally located on logical unit 16. During normal operation ofsystem 10, server 22 periodically copies data located on logical unit 16to storage device 24 so that back up copies of the data may be availableto host 20. Agent module 32 instructs server 22 to restore the data byaccessing storage device 24 and transferring the backup data from thelast backup of the failed logical unit to a newly configured sparelogical unit. In one embodiment, agent module 32 directly transfers thebackup data on storage device 24 associated with the failed logical unitto the spare logical unit. In an alternative embodiment, agent module 32may map the spare logical unit to server 22, and instruct server 22 tolocate the backup data associated with the failed logical unit onstorage device 24 and transfer the backup data to the spare logicalunit.

When the backup data has been restored on the spare logical unit, agentmodule 32 maps the spare logical unit to host 20 by assigning theaddress associated with the failed logical unit to the spare logicalunit. For example, in a SAN using fibre channel protocol, host 20 may beidentified by a WWN. Agent module 32 initially maps logical unit 16 tohost 20 by specifying the WWN for host 20. If a failure occurs atlogical unit 16, agent module 32 restores the backup data from logicalunit 16 by using logical unit 18 and maps logical unit 18 to host 20 byassigning the host WWN associated with logical unit 16 to logical unit18. The agent configures logical unit 18 such that logical unit 18appears to host 20 as logical unit 16.

In one embodiment, host 20 may be executing an operating system thatmust be rebooted before host 20 can access the restored data on logicalunit 18. In this case, agent module 32 generates a message thatinstructs host 20 to reboot. In one embodiment, host 20 includes a hostagent that may receive an instruction to automatically reboot host 20 sothat host 20 may begin to use the spare logical unit to store and accessdata. The host agent may also send a notification to a systemadministrator located at an administration terminal that host 20rebooted due to a failure at logical unit 16. In another embodiment,agent module 32 sends notification to the system administratorindicating that a failure occurred at storage device and that host 20should be rebooted. In this example, the system administrator manuallyreboots host 20 to create a link between the spare logical unit atstorage device 14 and host 20.

FIG. 3 illustrates a flow diagram for providing automatic datarestoration after a storage device failure. Generally, agent module 32located in SAN appliance 12 detects when a logical unit, such as logicalunit 16, that is located on storage device 14 and assigned to host 20has failed. In response to detecting the failure, agent module 32configures a spare logical unit, such as logical unit 18, transfersbackup data located on storage device 24 and associated with the failedlogical unit to the spare logical unit and maps the spare logical unitto host 20 by using a host address assigned to the failed logical unit.In a particular embodiment, agent module 32 restores normal operation ofsystem 10 by rebooting host 20 to create a logical link between host 20and the spare logical unit.

At step 40, system 10 is operating under normal conditions. Under normalconditions, host 20 accesses logical unit 16 at storage device 14 tostore and retrieve data used by host 20 to execute a variety ofapplications. During this time, server 22 accesses storage device 14 toperiodically transfer the data from logical unit 16 to storage device24.

At step 42, agent module 32 monitors storage device 14 for failures thatmay occur at logical units 16. If agent module 32 does not detect anyfailures, system 10 continues normal operations at step 40. If agentmodule 32 detects a failure at a logical unit being used by host 20,agent module 32 configures a spare logical unit at step 44. For example,host 20 may be assigned to use logical unit 16 from storage device 14.Agent module 32 may receive a message from storage device 14 that afailure has occurred at logical unit 16. The message may be sent to SANappliance 12 using SNMP, XML or any other protocol that allowscommunication to occur in a distributed environment. In one embodiment,agent module 32 requests a spare logical unit from storage device 14. Inthis case, the spare logical unit is configured (e.g., logical unit 18)and storage device 14 gives agent module 32 access to the configuredlogical unit. In an alternative embodiment, the spare logical unit maynot be configured and storage device 14 may create one. In this example,storage device 14 creates the spare logical unit from disks, tapedrives, optical or magnetic media or other storage media not in use tomeet the size requirements indicated by agent module 32. In a furtherembodiment, logical unit 18 may be configured on a storage deviceseparate from storage device 14.

At step 46, agent module 32 locates server 22 and/or storage device 24.In one embodiment, agent module 32 requests server 22 to provide thelocation of the data copied or backed up from logical unit 16 so thatagent module 32 may directly transfer the backup data to the sparelogical unit (e.g., logical unit 18). In another embodiment, agentmodule 32 may not have the capability to directly transfer data and maymap logical unit 18 to server 22. At step 48, the backup data associatedwith logical unit 16 is transferred from storage device 24 to logicalunit 18. In one embodiment, agent module 32 may directly transfer thebackup data by obtaining the location of the backup data on storagedevice 24 from server 22. In an alternative embodiment, server 22 mayperform the data transfer. In this example, agent module 32 maps logicalunit 18 to server 22 by specifying an address associated with logicalunit 18 and instructs server 22 to transfer the backup data obtainedfrom logical unit 16 and located on storage device 24 to logical unit18.

At step 50, agent module 32 determines if the backup data restoration iscomplete. If the restoration is not complete, agent module 32 continuesto transfer backup data from storage device 24 to logical unit 18 atstep 48. If the data restoration is complete, agent module 32 mapslogical unit 18 to host 20 and a host address assigned to logical unit16 at step 52. In one embodiment, the address may be an eight byte WWN.In alternative embodiments, the address may be an IP address, anEthernet address or any other suitable address that identifies thelocation of host 20 on network 26.

After logical unit 18 is mapped to host 20, agent module 32 creates alogical link between host 20 and logical unit 18. At step 54, agentmodule 32 determines if the operating system being executed on host 20requires a reboot to access the data on logical unit 18. If theoperating system does not require a reboot, host 20 has access to thedata on logical unit 18 and system 10 returns to normal operation withhost storing data on and retrieving data from logical unit 18 at step40.

If the operating system requires a reboot, agent module 32 determines ifhost 20 includes a host agent that may automatically reboot host 20 atstep 56. If agent module 32 does not detect the host agent, agent module32 sends a message to a system administrator to reboot host 20 at step58. The message may be an SNMP alert, email message or any othersuitable message that may be displayed on a stand-alone PC, workstationor any other device operable to display information from network 26. Atstep 60, the system administrator manually reboots host 20. After thereboot is complete, system 10 returns to normal operation at step 40. Ifagent module 32 detects the host agent on host 20, agent module 32instructs the host agent to reboot host 20 at step 62. After host 20 isrebooted, a logical link is established between host 20 and logical unit18 and system 10 returns to normal operation.

Although the disclosed embodiments have been described in detail, itshould be understood that various changes, substitutions and alterationscan be made to the embodiments without departing from their spirit andscope.

1. A computer system, comprising: a host operable to interface with anetwork; a primary storage device operable to interface with thenetwork, the primary storage device including first and second logicalunits, the first logical unit assigned to store data generated by thehost; and an agent module operable to communicate with the host and theprimary storage device, the agent module further operable to: detect afailure at the first logical unit; locate backup data from the firstlogical unit on a backup storage device; transfer the backup data fromthe backup storage device to the second logical unit; map the secondlogical unit to a host address associated with the first logical unit inresponse to detecting the failure at the first logical unit; andinstruct the host to reboot after the second logical unit has beenmapped to the host.
 2. The computer system of claim 1, wherein theprimary storage device comprises a redundant array of independent disks(RAID) device.
 3. The computer system of claim 1, wherein the detectingcomprises receiving notification from the primary storage device of thefailure at the first logical unit.
 4. The computer system of claim 1,wherein the address comprises a world wide name (WWN).
 5. The computersystem of claim 1, wherein the backup storage device comprises a tapedrive.
 6. The computer system of claim 1, further comprising the agentmodule operable to configure the second logical unit in response todetecting the failure.
 7. The computer system of claim 1, wherein thenetwork comprises a fibre channel network.
 8. A computer system forproviding automatic data restoration after a storage device failure,comprising: a plurality of servers operable to interface with a network,the servers including an application server and a backup server; aplurality of storage devices operable to store data associated with theservers, the storage devices including an application storage deviceincluding first and second logical units and a backup storage deviceinterfaced with the backup server, the first logical unit assigned tothe application server by using a first logical unit number (LUN)address; and an agent module associated with the servers and the storagedevices, the agent module operable to: detect a failure at the firstlogical unit; assign the second logical unit to the backup server inresponse to detecting the failure; instruct the backup server totransfer backup data associated with the first logical unit from thebackup storage device to the second logical unit; map the second logicalunit to the application server when the backup data transfer from thebackup storage device is complete by using a second LUN addressassociated with the second logical unit and a server address associatedwith the application server; and instruct the application server toreboot after the second logical unit has been mapped to the applicationserver.
 9. The computer system of claim 8, wherein the applicationstorage device comprises a RAID device.
 10. The computer system of claim8, wherein the backup storage device comprises a tape drive.
 11. Thecomputer system of claim 8, further comprising the agent module operableto configure the second logical unit in response to detecting thefailure at the first logical unit.
 12. The computer system of claim 8,wherein the network comprises a fibre channel network.
 13. A method forproviding automatic data restoration after a storage device failure,comprising: detecting a failure at a first logical unit operable tostore data associated with a host, the host operable to couple to anetwork; configuring a second logical unit in response to detecting thefailure at the first logical unit, the first and second logical unitslocated on a first storage device operable to couple to the network,wherein: the first device comprises a RAID device; and whereinconfiguring the second logical unit in response to detecting the failureat the first logical unit comprises instructing the RAID device tocreate the second logical unit from one or more spare storage media;transferring backup data associated with the first logical unit from asecond storage device to the second logical unit; and mapping the secondlogical unit to a host address associated with the first logical unitwhen the backup data transfer from the second storage device iscomplete.
 14. The method of claim 13, further comprising: communicatingthe data between the host and the first logical unit via the network;and communicating the backup data between the first logical unit and thesecond storage device via the network.
 15. The method of claim 13,further comprising locating the backup data associated with the firstlogical unit on the second storage device, the backup data copied fromthe first logical unit to the second storage device prior to thefailure.
 16. The method of claim 13, wherein the second storage devicecomprises a tape drive.
 17. The method of claim 13, further comprisinginstructing the host to reboot after mapping the second logical unit tothe host.
 18. The method of claim 13, wherein the transferring comprisesinstructing a backup server interfaced with the second storage device tocopy the data from the second storage device to the second logical unit.19. The method of claim 13, wherein the detecting comprises receiving anSNMP message.
 20. The method of claim 13, further comprisingcommunicating the data via a fibre channel network.
 21. A method forproviding automatic data restoration after a storage device failure,comprising: detecting a failure at a first logical unit operable tostore data associated with a host, the host operable to couple to anetwork; configuring a second logical unit in response to detecting thefailure at the first logical unit, the first and second logical unitslocated on a first storage device operable to couple to the network;transferring backup data associated with the first logical unit from asecond storage device to the second logical unit; mapping the secondlogical unit to a host address associated with the first logical unitwhen the backup data transfer from the second storage device iscomplete; and instructing the host to reboot after mapping the secondlogical unit to the host.
 22. A method for providing automatic datarestoration after a storage device failure, comprising: detecting afailure at a first logical unit operable to store data associated with ahost, the host operable to couple to a network; configuring a secondlogical unit in response to detecting the failure at the first logicalunit, the first and second logical units located on a first storagedevice operable to couple to the network; transferring backup dataassociated with the first logical unit from a second storage device tothe second logical unit, wherein the transferring comprises instructinga backup server interfaced with the second storage device to copy thedata from the second storage device to the second logical unit; andmapping the second logical unit to a host address associated with thefirst logical unit when the backup data transfer from the second storagedevice is complete.